. Bulletin of the British Museum (Natural History), Geology. Fig. 13 Camera lucida drawings of plating in Orthopsis miliaris (d'Archiac). A, apical disc plating, BMNH EE3723; B, ambital ambulacral (left) and interambulacral (right) plates, BMNH EE3723; C, adoral plating, ambulacrum to left, interambulacrum to right, BMNH EE3733. Scale bars: A, B = 1 mm; C = 2 Fig. 14 Camera lucida drawings of lantern elements in Orthopsis miliaris (d'Archiac): A-D, BMNH EE3735; E, BMNH EE5020. A, pyramid with rotula and tooth in position; B, same in lateral view; C, fragment of compass element; D, adapica
. Bulletin of the British Museum (Natural History), Geology. Fig. 13 Camera lucida drawings of plating in Orthopsis miliaris (d'Archiac). A, apical disc plating, BMNH EE3723; B, ambital ambulacral (left) and interambulacral (right) plates, BMNH EE3723; C, adoral plating, ambulacrum to left, interambulacrum to right, BMNH EE3733. Scale bars: A, B = 1 mm; C = 2 Fig. 14 Camera lucida drawings of lantern elements in Orthopsis miliaris (d'Archiac): A-D, BMNH EE3735; E, BMNH EE5020. A, pyramid with rotula and tooth in position; B, same in lateral view; C, fragment of compass element; D, adapical view of pyramid, with proximal end of tooth (broken) towards the top; E, cross-section of a single tooth. Scale bars = 1 mm. uniserially or in very weak arcs of three (PI. 3, fig. 6). All ambulacral elements are narrow and elongate and reach the perradius (Fig. 13B). A primary tubercle (perforate and non-crenulate) straddles two of the three elements in each compound plate (PI. 3, fig. 6). The third element carries two small secondary tubercles and an intermediate row of miliary granules. There are secondary and miliary tubercles down the perradius also. Adorally only the first five or so pore-pairs are offset to form a weak phyllode (Fig. 13C). There are 55 pore-pairs in a column at 20 mm test diameter, rising to around 90 at 46-48 mm diameter (Fig. 12). Sphaeridial pits are very shallow and are present on the two or three most adoral compound plates, immediately adjacent (perradial) to the pore-pair on the element in each triad that does not support a primary tubercle. Interambulacra are 38^14% of the test diameter in width at the ambitus (mean = 41%, SD = 2-0%, N = 11) (Fig. 12). Ambital plates are short and wide and slightly curved. At the ambitus most specimens have a single primary tubercle, centrally positioned, plus two smaller secondary tubercles one on either side (PI. 3, figs 3, 8; Fig. 13B). However, in a fragment of a large specimen (ca. 65 mm diameter, BMNH EE37
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